It is well recognized that amorphous polypropylene(aPP) is a soft, rubbery, gel-like material which possesses very low crystallinity and therefore poor physical properties. Because of its poor mechanical strength, this material has found few practical uses compared to other forms of polypropylene such as isotactic polypropylene(iPP) and syndiotactic polypropylene (sPP), both of which are crystalline and therefore have good mechanical properties.
Individual polyolefins having certain characteristics are often blended together in the hopes of combining the positive attributes of the components. Typically, however, the result is a blend which displays a weighted average of the individual properties of the individual resins. For example European Patent Application 0 527 589 published Feb. 17, 1993, blends flexible low molecular weight amorphous polypropylene (aPP) with higher molecular weight stiff and strong isotactic polypropylene (iPP) to obtain compositions with balanced mechanical strength and flexibility. The composition shows better flexibility compared to the isotactic polypropylene but the elastic recovery properties are still poor. Yet it is desirable to find a composition that is both very flexible and very strong. It is an object of this invention to provide such a composition.